1. Field of the Invention
Embodiments of the invention described herein relate generally to limb-motion detection and, in particular, limb-motion detection using a plurality of sensor signals.
2. Description of the Related Art
Millions of individuals worldwide rely on prosthetic and/or orthotic devices to compensate for disabilities, such as amputation or debilitation, and to assist in the rehabilitation of injured limbs. Orthotic devices include external apparatuses used to support, align, prevent, protect, correct deformities of, or improve the function of movable parts of the body. Prosthetic devices include apparatuses used as artificial substitutes for a missing body part, such as an arm or leg.
Conventional orthoses are often used to support a joint, such as an ankle or a knee, of an individual, and movement of the orthosis is generally based solely on the energy expenditure of the user. Some conventional prostheses are equipped with basic controllers that artificially mobilize the joints without any interaction from the amputee and are capable of generating only basic motions. Such basic controllers do not take into consideration the dynamic conditions of the working environment. The passive nature of these conventional prosthetic and orthotic devices typically leads to movement instability, high energy expenditure on the part of the disabled person or amputee, gait deviations and other short- and long-term negative effects. This is especially true for leg orthoses and prostheses.
To address these drawbacks, some prosthetic devices include one or more systems for monitoring the movement of a user. For instance, certain prosthetic knee devices include one or more pressure sensors implanted in an insole for detecting changes in force during user movement. In response to these detected changes in force, a control unit mechanically adjusts the prosthetic knee. Such measurements, however, are generally usable only for analysis of the past gait of the user. Furthermore, because the pressure sensors are generally used to detect contact between the foot and the ground, the pressure sensors are not able to produce usable signals during a swing stage of the foot. In addition, the insole containing the pressure sensors often requires precise placement and alignment in relation to the limb being monitored.